Fiber optic cables are used for high speed data transmission in many applications. This includes long distance telecommunications and computer networks, and smaller networks such as those used on advanced aircraft. Typically, a fiber optic cable carries a signal from a remote emitter, to be received by a detector on an electronic instrument such as a computer, relay station, communications hub, or the like. The fiber must be terminated in a manner that couples the light onto a photodetector and/or coupled light from the light source (laser or LED array) into the fiber. Such terminal elements may include lenses that receive the light signal from the light source and focus it onto the fiber or receive the light from the fiber, and focus it onto the receptor. In many applications, multiple independent fibers will carry independent signals, and the terminal will have several lenses to focus the beams from several emitters onto their respective fibers or from several fibers onto a corresponding array of detectors.
Some applications such as outdoor communications hubs and military hardware require environmental seals, often hermetic, to prevent damage, performance degradation, and premature failure due to harsh environmental conditions. This presents a significant challenge for fiber optic terminations, which are analogous to collimated flash lights positioned with micron-level precision. The termination must provide optical coupling, provide mechanical strain relief and often must provide a hermetic seal. Typical hermetically sealed components are bulky, making miniaturization of fiber optic terminal elements difficult. Moreover, hermetic seals often employ rigid materials that create a stress point where the fiber enters the material, making the fiber susceptible to damage, degradation, and breakage.
Miniaturization is particularly important in avionic and other mobile systems where size and weight are significant constraints. For example, it is highly desirable to pack as many system cards as possible into a rack to save space and weight. This can be accomplished by minimizing the height of electronic circuit boards electro-optic components such as emitters and detectors and the associated optical fiber interface. Optical fibers are made from glass and cannot be bent sharply without suffering optical loss or breakage. If the active area of the electro-optic device is coplanar with the circuit board to which it is mounted, then an optical component that folds the optical path is highly desirable. In addition, miniaturized parts have the added challenge of being more sensitive to misalignment, so that precision of manufacture and positioning during assembly is more critical. Consequently, there is a need for a readily manufactured fiber termination that is compact, low-profile, and can be precisely aligned.
Pertinent technology is disclosed in U.S. patent application Ser. No. 11/341,336, entitled “Hermetic Fiber Optic Ferrule”, filed Jan. 26, 2006 which is incorporated herein by reference.
There is a further need for multi-channel optical terminations that provide enhanced control over crosstalk, attenuation, filtering, and which may readily be manufactured without significant sensitivity to tolerance and alignment errors.